The present invention relates generally to crash impact attenuators, and more particularly to motor vehicle and highway barrier crash impact attenuators constructed from molded plastic materials.
Vehicular accidents on the highway are a major worldwide problem and are undoubtedly one of the largest causes of economic and human loss and suffering inflicted on the developed world today. In an effort to alleviate, in particular, the human toll of these tragic accidents, guardrails, crash cushions, truck-mounted crash attenuators, crash barrels, and the like have been developed to attenuate the impact of the vehicle with a rigid immovable obstacle, such as a bridge abutment.
Existing plastic impact attenuators, as described in U.S. Pat. No. 5,403,112, herein expressly incorporated by reference, comprise a row of plastic tubes with retention cables. A key feature of the units is the ability to survive impact and recover to near original shape—minimizing maintenance costs. However, these existing systems, comprising an array of polyethylene cylinders attached to one another in some fashion, have a number of significant disadvantages. They are labor-intensive to assemble and material-intensive. With respect to force-deflection characteristics, existing designs are undesirable since the force increases continuously with deformation. The force cannot exceed the light vehicle limit, and therefore the initial force and deceleration is low, limiting the initial energy absorption.
With respect to maximum deformation characteristics, existing plastic attenuation systems are not ideal. A cylinder, when flattened, has extreme deformation at the outer edges so the recovery to original shape is difficult.
A crash attenuator of the type described must absorb the vehicle impact energy without exceeding limits on the vehicle deceleration. In addition, it must accommodate both heavy and light weight vehicles. The lightest vehicle will set the limit on the maximum force produced by the attenuator and the heavy vehicle—which will experience a lower deceleration, and thus will determine the total impact deformation required. The force cannot exceed the light vehicle limit and therefore the initial force and deceleration is low, limiting the energy absorption.